The mental equilibrium of many backward peoples is very unstable, although they may not suffer from the same derangements of the nervous system that affect the more highly civilised peoples. To take an example or two of this =nervous instability=, Castren observed long ago that if the Samoyeds were sitting around inside their skin tents in the evening, and some one crept up and struck the tent, half of them were likely to fall into cataleptic fits. Bogoras (5, 42) refers to the well-known Arctic hysteria which is so widespread among the Yukaghir and Lamut women, and to a less extent among the Chukchee, the Russianised, and even the Russian women. This disease develops chiefly in the form of an uncontrollable desire to repeat in a loud voice each word spoken by somebody else, and to imitate every sudden gesture or action. This is the same nervous disorder as the widely spread _lâtah_ of Malaysia, which has been so admirably described by Sir F. A. Swettenham (68, 64). The far-reaching power of =suggestion= has been perhaps the most potent factor in upholding magical practices, especially when it is =combined with hypnotism=. The hypnotic state, it must be remembered, though ordinarily produced by another, can be self-induced by gazing at an object. There is an overwhelming number of modern instances of bad habits, various diseases, inflammations, local and general pain, insomnia, neurasthenia, psychic paralysis, and psychic hysteria, being cured by suggestion while the patient is in the hypnotic state (31, 607). Conversely pain, inflammations, and other organic changes can be produced through the same means; such is the explanation of the appearance of stigmata on the hands and feet of religious ecstatics, who had induced auto-hypnotism by intently gazing on the Figure on the Cross. The cataleptic and anæsthetic conditions producible by hypnotism are well known all over the world, and have for ages been part of the stock-in-trade of sorcerers, medicine-men, or of certain religious enthusiasts. =Suggestion alone=, without the aid of hypnotism, can effect wonders, and faith-cures and Christian science are by no means a new thing under the sun, but something very old under new names. Probably every physician has known cases of ‘persons who died because they did not want to live or were at least indifferent; and probably an equal number who materially lengthened their lives by the mere determination not to die’ (67, 612).